The conjugacy of geomagnetic phenomena at high latitudes in the northe
rn and southern hemispheres is investigated using observations of the
geomagnetic field variations. Similar the magnetic disturbances at the
poleward edge of the auroral oval night sector were observed in both
hemispheres. These results show that magnetic field lines at the perip
hery of the plasma sheet are closed and that processes leading to the
appearance of magnetic disturbances are similar in conjugate regions.
Modeling of geomagnetic field line structure has shown that field line
s are closed up to a distance of several dozens of Earth radii during
the existence of the tail current wedge. The region of closed field li
nes maps to the nightside ionosphere up to similar to 80 degrees geoma
gnetic latitude.